1. Field of the Invention
The present invention relates generally to a fiber optic distribution cable deployed in a fiber optic communications network and, more particularly, to a factory-prepared fiber optic distribution cable assembly having a flexible overmolded mid-span access location with a preferential bend.
2. Description of the Related Art
Optical fiber is increasingly being used for a variety of broadband applications including voice, video and data transmissions. As a result, there is a need for connecting remote locations to a fiber optic distribution cable in order to provide broadband services to an end user, commonly referred to as a subscriber. In this regard, fiber optic networks are being developed that deliver “fiber-to-the-curb” (FTTC), “fiber-to-the-business” (FTTB), “fiber-to-the-home” (FTTH) and “fiber-to-the-premises” (FTTP), referred to generically as “FTTx.” networks. To provide these services to the subscriber, FTTx networks must include a large number of interconnection points, referred to herein as “tap points,” at which one or more optical fibers of a distribution cable are interconnected or mated to optical fibers of one or more cables leading to a subscriber location. In addition, in order to reduce installation labor costs in FTTx networks, communications service providers are increasingly pre-engineering new fiber optic networks and demanding factory-prepared interconnection solutions, commonly referred to as “plug-and-play” systems.
To supply the large number of tap points needed and to satisfy the demand for plug-and-play systems, it is apparent that more efficient methods of providing mid-span access locations along the length of a distribution cable are needed. Presently, to perform a mid-span access of a distribution cable, a section of the cable sheath is removed at a predetermined location along the length of the distribution cable, thereby exposing a plurality of optical fibers disposed in buffer tubes that are helically wound within the cable. Once the section of cable sheath is removed, preselected optical fibers are severed and withdrawn from the distribution cable to produce one or more terminated optical fibers that are presented for splicing or interconnection at the tap point. Oftentimes, the terminated optical fibers are smoothly transitioned out of their respective buffer tube(s) and spliced to optical fibers of a length of tether cable that is attached to the distribution cable at the mid-span access location. After splicing is completed, the mid-span access location is typically covered using an overmolding process that protects the splices and the exposed section of the distribution cable resulting from the creation of a mid-span access location. In order to access a sufficient length of the optical fibers for splicing with the tether cable, the mid-span access location typically has a length up to about 36 inches.
By terminating the preselected optical fibers and transitioning them out of their respective buffer tubes and away from the distribution cable, the terminated optical fibers are routed along a path that is different than the path of the remaining optical fibers of the distribution cable. As the mid-span access location is bent, for example when rolled on a reel, pulled through a conduit having a bend, or pulled over an aerial installation pulley, path length differences may arise for the optical fibers terminated from the distribution cable. If the bending strain on the optical fibers is great enough, these path length differences may lead to attenuation, or in a worst case, the optical fibers may fail due to excessive axial tension stresses induced by bending. In addition to axial tension stresses on the optical fibers, tension stresses may also be placed on the overmolded mid-span access location at places where the overmold material is thinnest, leading to the sealing integrity of the overmold possibly being compromised. Specifically, the mid-span access location may have less overmold material at the top and bottom when the distribution cable and the tether cable are oriented one on top of the other. In other words, the overmolded mid-span access location has a generally tubular cross-sectional shape. If more than one cable (i.e., the distribution cable and the tether cable) is disposed within the mid-span access location, the thickness of the overmold material around all sides of the cables is not uniform, thus resulting in areas having lesser tensile strength.
There are several possible designs of mid-span access locations that address the problems described above associated with path length differences between the terminated optical fibers and the optical fibers remaining in the helically wound buffer tubes of the distribution cable. In one example, a rigid mid-span access location is provided to entirely eliminate bending of the mid-span access location. Obvious drawbacks to a rigid mid-span access location include the inflexibility to installation requirements and the increased diameter of a rigid mid-span access location. Another example is a mid-span access location that includes a slack storage region and/or generous passages within the mid-span access location to accommodate the path length differences between the terminated optical fibers and the remaining optical fibers that arise due to bending. However, the above examples result in a more complex arrangement having a larger cross-sectional area, thus resulting in installation inflexibility.
Accordingly, there is a specific and unresolved need for a factory-prepared fiber optic distribution cable assembly having one or more predetermined mid-span access locations along the length of a distribution cable for accessing and terminating a plurality of optical fibers, wherein each mid-span access location is provided with a preferential bend such that the terminated optical fibers are not subjected to undesirable axial tension loads induced by bending during normal handling and deployment. It is further desirable to provide a factory-prepared fiber optic distribution cable assembly having one or more predetermined mid-span access locations along the length of the distribution cable for accessing and terminating a plurality of optical fibers, wherein each mid-span access location is provided with a strength member or a geometric configuration to provide the mid-span access location with a preferential bend and an outer diameter that is only minimally larger than the outer diameter of the distribution cable. It would also be desirable to provide a fiber optic distribution cable assembly having one or more low-profile mid-span access locations that is sufficiently flexible to satisfy demanding installation requirements, such as through small-diameter conduits and over sheave wheels and pulleys.